The present invention relates to a method for converting a trialkylphenol, such as 2,4,6-trimethylphenol, or mesitol, to a dialkylphenol, such as 2,6-dimethylphenol, or 2,6-xylenol. More particularly, the present invention relates to a method for selectively oxidizing mesitol to 3,5-dimethyl-4-hydroxybenzaldehyde and thereafter effecting a deformylation of the benzaldehyde to produce 2,6-xylenol.
As shown by Talley, U.S. Pat. Nos. 4,533,767, 4,533,768, and 4,560,810, selective dealkylation of alkylated phenols can be achieved with steam in combination with various metal oxide catalysts, such as zinc oxide and optionally manganese oxide. Daly, U.S. Pat. No. 4,230,895 describes catalytic hydrodealkylation using mixtures of palladium and chromium oxide. Schnatterer U.S. Pat. No. 4,929,766 describes a process for converting p-cresol to p-hydroxy benzaldehyde employing oxygen in the presence of a solvent and a chelate complex of iron and/or manganese.
Although various techniques are available for dealkylating polyalkylated phenols, a satisfactory method for transforming a 2,4,6-trialkylphenol, such as mesitol, to 2,6-xylenol has not been developed. It would be a significant environmental advance if a method were developed to convert mesitol, which has limited utility and is often burned as a by-product to a useful end product, such as 2,6-xylenol, a key intermediate in the manufacture of polyphenylene oxide.